OBJECTIVE This project is a direct continuation of Research Project 1 in the ongoing Program Project Grant, and it represents the core interest of the Brown/Goldstein laboratory over the past 34 years. We are finally nearing our long-term objective, which is to gain a molecular understanding of the machinery that regulates the level of cholesterol in blood and in cells. We believe that this understanding will lead to more effective treatments for the pathologic blood lipoprotein levels that cause the vast majority of heart attacks and strokes. The early work provided the conceptual groundwork for the development of statins, the most widely prescribed class of drugs in the U.S., which have been demonstrated to reduce heart attacks and death from atherosclerosis. We believe that our current work will lead to even more effective therapies, not only for elevated blood cholesterol, but also for the lipid abnormalities associated with the looming epidemic of Type 2 diabetes. Central to these disorders is a family of membrane-bound transcription factors called Sterol Regulatory Element-Binding Proteins (SREBPs). Discovered in our laboratory in 1993, these proteins control the production of cholesterol and unsaturated fatty acids in liver and other tissues. The SREBPs, in turn, are tightly controlled by sterols and by insulin in a complex pathway that has taken us into unexplored avenues of cell biology and physiology. Our objective in the renewal grant is to complete this 34-year quest.